1. Field of the Invention
The present invention pertains to the art of testing devices for miniature electronic components and, more particularly, to a contact arrangement incorporated in a Kelvin testing device.
2. Discussion of the Prior Art
It is common practice to test the performance characteristics of miniature electronic components, such as semiconductors, prior to mounting of the components in electronic devices. For this purpose, leads of the miniature electronic components are electrically connected to a testing apparatus which generally applies a predetermined test current across respective lead pairs and measures a voltage drop associated with the component. The voltage drop is then compared to a predetermined specification in order to verify the quality of the component. Therefore, in order to test such miniature electronic components, the leads are engaged with contacts of the testing device in order to deliver the desired test current In such a testing device, a varying resistance can be created between the leads of the component being tested and the contacts of the testing device which can distort the measured voltage drop, particularly when components requiring relatively large currents are being tested. To avoid such testing errors, the use of Kelvin-type contacts have become widely accepted in the art.
In general, Kelvin contacts are arranged in sets, each of which includes a current supply contact and a voltage transmitting contact. More specifically, the current supply or "forcing" contact is adapted to engage one part of a lead of an electronic component to be tested while the voltage transmitting or "sensing" contact also engages the same lead. With such an arrangement, the sensing contacts receive a very small flow of current and therefore the voltage drop due to contact resistance is minimal, thereby enabling an accurate test reading.
Kelvin contact-type testing devices known in the art generally take two forms. In one form, the testing lead is pressed between the forcing and sensing contacts. More specifically, the electronic component to be tested is placed within a Kelvin testing device with each lead initially engaging a lower testing contact and then a unit is activated to shift a movable portion of the testing device such that an upper Kelvin contact engages the same lead, with the lead being clamped between the upper and lower Kelvin contacts. Obviously, such a testing arrangement requires additional time for actuation of the clamping arrangement such that testing of the electronic components in this fashion is rather time consuming and significantly slows down production. This particular type of testing device also suffers from the need to have a precise alignment of the electronic component within the testing device or else damage can be done to one or more of the leads and/or contacts during the clamping operation.
A second type of known Kelvin contact-type testing device positions the forcing and sensing contacts in a slightly spaced, side-by-side arrangement, thereby locating the contacts in a common, generally horizontal plane. In accordance with this type of testing arrangement, an electronic component need merely be brought vertically into engagement with the adjacent Kelvin contacts, with each of the contacts engaging a single side of a respective lead of the electronic component Although this style of testing device avoids the potential for damage due to any clamping action, even higher degrees of precision alignment must be established to assure a good engagement between the lead and the contacts. However, the leads on various miniature electronic components, such as many semiconductors, are so small in width that utilizing Kelvin contacts arranged side-by-side is not feasible.